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Biologists have explored how testate amoebae survive in peat fires

19.06.2017

Scientists have studied the impact of wildfire on testate amoebae

An International team from China University of Geosciences, University of York and Lomonosov Moscow State University have studied the impact of wildfire on testate amoebae -- one of the dominant microbial groups in peat bogs. The biologists' research has been published in the peer-reviewed journal Applied Soil Ecology.

The testate amoebae Lesquereusia epistomium is pictured.

Credit: Yuri Mazei

Testate amoebae significantly affect biochemical processes in peatland ecosystems. However, little is known about the effect of such wildfires on microbial components of bog ecosystems.

Testate amoebae are unicellular organisms, largely enclosed by a shell. They comprise up to half of all microbial biomass in peatlands. Changes in their community structure under fire exposure can have significant impacts on the structure of food webs since alteration of one important food web component influences all the others. Presence of testate amoebae in a local ecosystem also has an effect on intensity of the silicon cycle.

Silicon is the second (after oxygen) most common chemical element in the crust of the Earth. However, only a few organisms have learnt to include this inorganic silicon into their cell composition, using it as a material of construction and also for performing many physiological functions. Some groups of testate amoebae (namely, that ones, which use silica plates for making their shells, laying these plates on the surface of the shell like roof tile) could "dissolve" solid silicon-containing components from the environment and produce out of them plates, used for constructing their shells. In other words, testate amoebae constitute one of the links in the silicon cycle.

The scientists chose a peatland in the northeast China, exposed to wildfire several years ago, as an object of research. The territory investigated consisted of heavily and slightly burned areas (due to the fact that firemen managed to put out a fire on a part of the bog). This provided the opportunity to compare communities of testate amoebae from parts exposed and non-exposed to fire.

It was found out that fire led to significant changes in the structure of the testate amoeba community. That microorganisms, which make their shells out of sandgrains, survived, while, the others, using silica plates synthesized inside the cells to make the shells, died. The scientists assumed that amoebae, making their shells out of sandgrains, are more resistant to high temperatures, since their shells are thicker and more solid due to these grains of sand.

Professor Yuri Mazei from the Department of Hydrobiology at the Faculty of Biology of the Lomonosov Moscow State University has described the method of investigation of testate amoebae:

"At first testate amoebae are separated from a soil or moss substrate. After that the flask with this suspension is intensively shaken up and passed through a number of filters so that only amoebae shells and small suspended particles are left. Afterwards, the final filtrate is put under a light microscope. Sometimes scientists use a scanning electron microscope in order to identify species."

Researchers from the Lomonosov Moscow State University, the University of Yorkand the University of Penza have previously proved that studies of testate amoebae's communities could be an effective tool for reconstructions of climatic changes in the past. The results obtained in this study will also allow the consideration of modern processes when conducting paleoecological reconstructions in burned peatlands.

Yuri Mazei comments on the project results: "In peatland columns there are often layers, containing charcoal, showing that the ecosystem burned at that time and these layers can contain testate amoebae. However, if you want to correctly reconstruct climate in such a layer, it's necessary to understand how testate amoeba communities respond to wildfire in current conditions. Our research has identified these peculiarities for the first time, which should improve existing approaches to palaeoreconstructions".

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